Stunting Sediment Causes Trouble for Fish

It may sound inconsequential, but sand and fine sediment from activates like sea-floor dredging and natural flood plumes can have a destructive impact on aquatic life. Now researchers are saying that silty deposits can even have a stunning impact on fish, extending the time required for the development of their larvae.

"Sediment concentrations at levels found in plumes from dredging or in floods cause a significant delay in the development of clownfish larvae," Amelia Wenger of James Cook University in Australia said in a recent statement. "This in turn could significantly reduce the numbers of larvae competent to settle on reefs and could have a major effect on adult populations."

Wenger and her colleagues recently authored a study that was published in The Journal of Experimental Biology that details how fish larvae raised in even slightly elevated sediment took much longer to develop than those raised in the absence of sediment. In many cases, the development time of sample clownfish populations doubled from the normal 11 days to 22 days.

The exact cause for why this occurs remains unclear, but Wengner explains that a prolonged larval stage can have a drastic impact on how many fish actually make it to adulthood.

"The pelagic larval stage is when you get the highest level of mortality, so the longer fish spend as larvae the less likely they are to survive," she said. "During this time they can be in open water away from the protection of the reef so if a fish is spending twice as long in this stage it means their risk from predators is greatly increased," Dr Wenger says.

Co-author, Geoff Jones added that it remains unclear if all fish species are as vulnerable to the phenomenon as clownfish, but if changing flood patterns and increased dredging operations around the world continue, many ecosystems could be in serious danger.